[PATCH v4 2/8] wifi: brcmfmac: sdio: coalesce sdio_claim_host calls in rxglom path

[Shivesh <chanelshivesh@gmail.com>]

brcmf_sdio_rxglom() performs one sdio_claim_host()/sdio_release_host()
pair for the superframe header parse and then one additional pair for
every subframe header parse. For a superframe containing N subframes
this means N+1 mutex lock/unlock round-trips on the hot RX path.

Group all header parse calls — superframe and all subframes — under a
single claim/release pair. The host is still released before the
subsequent pure host-memory processing (skb_pull, len_nxtfrm update),
keeping the hold time as short as possible. The error path (rxfail)
also executes while the host is claimed, which is required because
brcmf_sdio_rxfail() writes SDIO Func1 registers.

Signed-off-by: Shivesh <chanelshivesh@gmail.com>
---
 .../broadcom/brcm80211/brcmfmac/sdio.c        | 62 ++++++++++++-------
 1 file changed, 38 insertions(+), 24 deletions(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
index b725c64e5b5c..4e414403d747 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
@@ -1645,37 +1645,43 @@ static u8 brcmf_sdio_rxglom(struct brcmf_sdio *bus, u8 rxseq)
 
 		rd_new.seq_num = rxseq;
 		rd_new.len = dlen;
+
+		/*
+		 * Claim the host once for the entire header-parsing phase.
+		 *
+		 * brcmf_sdio_hdparse() operates on data already in host
+		 * memory, but may call brcmf_sdio_rxfail() on error, which
+		 * writes SDIO Func1 registers and therefore requires the
+		 * host to be claimed.
+		 *
+		 * skb_pull() and the num counter are pure host-memory
+		 * operations; keep them outside the lock to minimise the
+		 * hold time.  Both hdparse calls (superframe header and
+		 * each subframe header) are grouped under a single claim/
+		 * release, replacing the original N+1 separate pairs.
+		 */
 		sdio_claim_host(bus->sdiodev->func1);
 		errcode = brcmf_sdio_hdparse(bus, pfirst->data, &rd_new,
 					     BRCMF_SDIO_FT_SUPER);
-		sdio_release_host(bus->sdiodev->func1);
-		bus->cur_read.len = rd_new.len_nxtfrm << 4;
-
-		/* Remove superframe header, remember offset */
-		skb_pull(pfirst, rd_new.dat_offset);
-		num = 0;
-
-		/* Validate all the subframe headers */
-		skb_queue_walk(&bus->glom, pnext) {
-			/* leave when invalid subframe is found */
-			if (errcode)
-				break;
 
-			rd_new.len = pnext->len;
-			rd_new.seq_num = rxseq++;
-			sdio_claim_host(bus->sdiodev->func1);
-			errcode = brcmf_sdio_hdparse(bus, pnext->data, &rd_new,
-						     BRCMF_SDIO_FT_SUB);
-			sdio_release_host(bus->sdiodev->func1);
-			brcmf_dbg_hex_dump(BRCMF_GLOM_ON(),
-					   pnext->data, 32, "subframe:\n");
-
-			num++;
+		/* Validate all the subframe headers while host is claimed */
+		if (!errcode) {
+			skb_queue_walk(&bus->glom, pnext) {
+				rd_new.len = pnext->len;
+				rd_new.seq_num = rxseq++;
+				errcode = brcmf_sdio_hdparse(bus, pnext->data,
+							     &rd_new,
+							     BRCMF_SDIO_FT_SUB);
+				brcmf_dbg_hex_dump(BRCMF_GLOM_ON(),
+						   pnext->data, 32,
+						   "subframe:\n");
+				if (errcode)
+					break;
+			}
 		}
 
 		if (errcode) {
-			/* Terminate frame on error */
-			sdio_claim_host(bus->sdiodev->func1);
+			/* Terminate frame on error, still holding the host */
 			brcmf_sdio_rxfail(bus, true, false);
 			bus->sdcnt.rxglomfail++;
 			brcmf_sdio_free_glom(bus);
@@ -1683,6 +1689,14 @@ static u8 brcmf_sdio_rxglom(struct brcmf_sdio *bus, u8 rxseq)
 			bus->cur_read.len = 0;
 			return 0;
 		}
+		sdio_release_host(bus->sdiodev->func1);
+
+		/* Host released; now do the pure-memory bookkeeping */
+		bus->cur_read.len = rd_new.len_nxtfrm << 4;
+
+		/* Remove superframe header, remember offset */
+		skb_pull(pfirst, rd_new.dat_offset);
+		num = 0;
 
 		/* Basic SD framing looks ok - process each packet (header) */
 
-- 
2.53.0